Replenishment systems

ABSTRACT

It is known to replenish processing solutions in photographic processing apparatus in accordance with the throughput of material being processed. However, in low usage apparatus, there is no allowance for other losses which may occur, for example due to evaporation and/or oxidation. Described herein is a method of replenishing such processing solutions which allows for losses due to evaporation and/or oxidation. The method comprises determining a relationship between loss rates due to evaporation and/or oxidation, and water evaporation rate from the apparatus. It has been found that the relationship is substantially linear.

The present invention relates to replenishment systems and is moreparticularly concerned with the replenishment of photographic processingsolutions in photographic processing apparatus.

Developers, and other solutions, used for photographic processing,suffer from depletion fog two principal reasons. The first is thatcomponents involved in the photographic process are used up assensitized material is passed through the solution, while the seconddepends on losses which occur without any processing taking place. Thelatter may be due, for instance, to aerial oxidation, evaporation, or aninteraction between components in the processing solution itself.

In a continuous photographic process, it is good practice to replenishsolutions, by replacing a proportion of the original solution withanother which has been formulated to replace those components which havebeen lost while reducing the level of unwanted by-products of theprocess.

Replenishment is normally carried out by adding a specially formulatedsolution to the bulk tank. This displaces a similar quantity of the usedsolution, at a rate which is calculated on the basis of the amount ofmaterial which has been processed. The assumption is made that otherlosses may be roughly accounted for at the same time.

For processes which have a low relative rate of usage, however, such anassumption is scarcely valid, and those losses which are independent ofmaterial throughput become very important. This means that adequatereplacement must be provided separately.

One solution to the problem has been to use a second replenisherdelivered at a rate which is proportional to elapsed time. Such systemsare disclosed in Japanese Patent Specifications 57-195245, 57-195246,57-195247, and U.S. Pat. Nos. 4,228,234, 4,245,043, 4,293,211,4,295,729, 4,329,042, 4,346,981, 4,372,665, and 4,372,666.

In U.S. Pat. Nos. 4,293,211, 4,295,729, 4,346,981, 4,372,665 and4,372,666, replenishment of anti-oxidants is disclosed. In particular,replenishment is carried out at two rates, a first rate whichcompensates for use of the processing apparatus, and a second lower ratewhich compensates for non-use of the apparatus. However, in each case,the replenishment is a function of expired time and is related to theparticular apparatus used.

In U.S. Pat. Nos. 4,245,043 and 4,329,042, the use of two replenishersand water is disclosed. The replenishers are added to the processingapparatus at one rate in accordance with the throughput of materialbeing processed. The same replenishers are used to replenish at a secondrate to compensate for non-use of the apparatus.

U.S. Pat. No. 4,228,234, describes a time-dependent replenishment systemin which the rate of replenishment is dependent on time, ambienttemperature and a constant which is related to the specific apparatusbeing replenished. This means that before being able to use thedisclosed system for other apparatus, the constant has to be determinedthrough experiment.

Furthermore, the systems described above do not accurately allow fordifferences in temperature between start-up conditions and operatingconditions.

It is therefore an object of the present invention to provide areplenishment system which allows for the replenishment of solutionsused in processing apparatus which suffer losses due to evaporation oroxidation, and which overcomes the problems associated with knownreplenishment systems.

According to one aspect of the present invention, there is provided amethod of replenishing photographic processing solutions in photographicprocessing apparatus in which one or more components are lost from theprocessing solution by oxidation or evaporation, characterized in thatthe replenishment rate for a particular component in a given solution isdetermined as a function of water evaporation rate from the apparatus.

Advantageously, the function for any given solution is determined bymeasuring component loss rates for that solution for different waterevaporation rates.

By this method, once the loss rate for a particular component in asolution has been determined, this rate can be applied to any processingapparatus using the same solution.

The present invention will now be described, by way of example only,with reference to the accompanying drawings, in which:

FIG. 1 shows the relation between benzyl alcohol loss rate and waterevaporation rate;

FIG. 2 shows the relation between hydroxylamine loss rate and waterevaporation rate;

FIG. 3 shows the relation between sulphate loss rate and waterevaporation rate; and

FIG. 4 is a control plot of one run showing the sensitometric effects.

Chemical loss rates were measured in a variety of processing machines ofdifferent types and having different developer tank volumes. Chemicalloss rates were also measured in laboratory standing tests. In thesestanding tests, containers having a volume of 11 with a range ofsurface/volume ratios were used. The chemical loss rates can bedetermined by using an `effective surface/volume` ratio.

Since the relative humidity, the air-space, the airflow, and thesolution surface agitation vary in the tests mentioned above, thegeometrical surface/volume ratio is not adequate to estimate oxidativeor evaporative loss rates of volatile components.

The `effective surface/volume` ratio will be generally higher than thegeometrical surface/volume ratio and can be estimated by measuring thewater evaporation rate/volume ratio, that is, the effectivesurface/volume is directly proportional to the water evaporationrate/volume.

The efficiency of this ratio can be tested by plotting the oxidative andevaporative loss rates against water evaporation rate/volume ratio. Inaddition, the effect of temperature change can be accounted for in thesame way since loss rates and evaporation rates change in the samedirection with temperature.

The rate of addition of time dependent replenisher (TDR) to a particularprocessing machine depends on the loss rates of the various components.It is possible by measuring loss rates as a function of time and theamount of sensitized material which is processed to construct a computermodel of a particular process in a particular machine. It is possiblefrom this model to predict the composition and rate of addition of theTDR to be used. Unfortunately, there are many different types ofprocessor in use and it would be difficult to model all these. However,five different types have been modelled and the rates of TDR additioncalculated.

It can be seen in Table 1 from the relation between the machine tankvolume (V) and the TDR rate (R) that the ratio R/V is approximatelyconstant for five different machines.

                  TABLE 1                                                         ______________________________________                                        Tank volume and TDR rate                                                      Machine   V (1)        R (ml/hr) R/V                                          ______________________________________                                        1         44           61        1.39                                         2         70           104.3     1.49                                         3         660          964       1.46                                         4         40           64.3      1.60                                         5         40           60.3      1.51                                         ______________________________________                                    

The mean value of R/V is 1.49 with a standard deviation of 0.076. Thismeans that to a first approximation the rate of TDR addition (ml/hr) canbe calculated from the processor developer-tank volume in litresmultiplied by 1.49.

The reason for this simple relation is that the total surface to volumeratio of these five machines is similar and so the loss rates per unitvolume are similar. Consequently the larger the volume the greater theaddition rate.

If processing machines have very different surface to volume ratios thenthe simple relation in Table 1 might not hold. In addition the meaningof surface to volume ratio is complex if absorbent rollers arecontinually turning and exposing fresh solution surface to the air.

One way to estimate a `true surface to volume ratio` is to use the waterevaporation rate which should be related to the geometrical surface tovolume ratio plus the effects of rollers and surface agitation.

It was found that this worked well and small bench top expertments with300 ml to 11 of solution gave similar results to large processingmachines. This also worked for processing solutions at differenttemperatures.

FIG. 1 shows the relation between benzyl alcohol loss and waterevaporation rate/volume for a variety of developer formulae,surface/volume ratios, and temperatures. The correlation coefficient is0.968. The data is derived from laboratory standing tests and commercialprocessing machines. The relation is linear and passes through theorigin.

Consequently, the water loss rate divided by the developer tank volumecan be used to estimate the chemical and evaporative loss rates in aprocessing machine for which no loss data is available, or which isbeing run at a different temperature, or both.

In FIGS. 2 and 3 similar relationships are shown for hydroxylamine lossand sulphite loss respectively. These do not correlate quite as well asbenzyl alcohol because there is some anaerobic reaction withhydroxylamine and sulphate which does not depend on surface area.

In addition, these two components are lost by chemical reactions whichcan be catalysed by traces of heavy metal ions such as iron and copperand these ions might, in practice, be present in variable amounts due tovariations in water-and chemical sources. This means that the plots ofchemical loss rate against water loss rate are probably not straightlines but some more complex function and also have intercepts indicatingsome chemical loss even at zero water loss. This is probably true forFIGS. 2 and 3 even though straight lines are shown.

In the case of benzyl alcohol the loss is almost solely by evaporationand therefore a better correlation would be expected.

In spite of these imperfections it is possible to estimate the loss rateof a volatile component or one which is lost by oxidation for an unknownmachine simply by measuring its evaporation rate in ml/hr and the tankvolume. This constitutes one of the main novel features of thisinvention. Evaporation rate must be measured under realistic conditions,that is, as the processor would normally be run with lids in place andup to temperature.

Similar relationships exist for the other components of photographicprocessing solutions, and, coupled with the knowledge of the tank volumeand measurement of the water evaporation rate, these relationships canbe used to calculate replenishment rates in an otherwise unknown system.

Ultimately it is desirable to control each component of the processindividually. This would require a control unit capable of calculatingthe absolute rates of loss for each component, and a dispenser--operatedby that controller--which would add components as powders, liquids, oras concentrates, and dissolve or disperse them in situ.

For any particular sensitized material the rate of loss of componentscaused by the processing of the material is essentially proportionalonly to the area of materials used--and over the normal range ofprocessing conditions both the solution temperature and the machineconfiguration can be disregarded. Thus, for any particular material, areplenisher can be formulated to be applied at a predetermined rateproportional to the area throughput.

In order to maintain solution concentrations accurately, it is importantto consider the matter of topping-up a tank with water to replace thatwhich has evaporated. In general, any replenisher could be formulatedwith only those components which must be replaced--in which case it mustbe added to the tank before topping-up--or it could be formulated withthose same components in addition to the preferred tank startingformula--in which case it should be added after topping-up, so that usedsolution is displaced.

The losses due to evaporation and oxidation are dependent on time and soare ideally made good by addition of TDR. The losses of chemicalcomponents due to usage by the sensitized material also need to be knownif a complete model of the replenishment system is to be made. Theselosses depend primarily on the nature of the sensitized material and notsignificantly on the type of processing machine. Thus, once these areknown, the procedure outlined in this specification can be used toestimate the evaporative and oxidative losses and a complete chemicalloss assessment can be made for a processor on which there was noexperience of running the formula.

There are three main ways in which the TDR principle can be applied inpractice as outlined in cases 1 to 3 below:

Case 1: TDR and PDR (paper dependent replenisher) which are different incomposition and in which the PDR is formulated primarily to account foruse up of chemicals by processed paper and TDR to account for the othertime dependent losses.

Case 2: TDR and PDR are different but the PDR is an existing replenisherused normally by itself at a higher utilization level or in a machinewith low oxidative and evaporative losses, but which can then be used ata lower utilization level in combination with a suitably formulated TDR(Example 1).

Cases 1 and 2 are referred to as Dual Mode Replenishment (DMR).

Case 3: TDR and PDR1 are the same formula and are used in combinationwith another solution which is the PDR2 consisting of colour developingagent and a small amount of preservative; PDR2 is added only as afunction of paper throughput. Although TDR and PDR1 are the same, thesolution is added both on a time dependent basis and on a paperthroughput dependent basis.

This case has been called Tri-Modal Replenishment (TMR).

In all these cases, the chemical loss rates can be determined by theprocedure outlined above and then it is a simple calculation to estimatethe composition of the TDR and PDR.

EXAMPLE 1

This example used EP-2 developer LORR in a Kreonite roller transportpaper processor. This particular version of EP-2 developer LORR wasdesigned for high utilization use in a non-roller transport deep tankmachine. The utilization used in this run was 5% which is low in thismachine and would not normally be recommended. It would be expected thatthe process activity would fall due to oxidation of colour developingagent because of loss of anti-oxidant protection under the harshconditions of a roller transport processor. A partial solution to thisproblem is to increase the replenishment rate; this increase howevermust be quite large to maintain satisfactory levels of the mainanti-oxidants, sulphate and hydroxylamine. Under these conditions thebromide level, anti-oxidant level and benzyl alcohol level would be lowand sensitometry would not be on aim. To overcome these problems asecond replenisher was used in addition to the normal replenisher whichcontained higher amounts of anti-oxidants. This is Case 2 as outlinedabove.

This second replenisher was added on a time dependent basis and isreferred to as a TDR. The composition of the paper dependent replenisher(PDR) and TDR are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                        Replenisher Compositions                                                      Component        TDR     PDR                                                  ______________________________________                                        TEA              6.20    4.25                                                 CD3              2.15    7.10                                                 BzOH             18.40   18.00                                                K.sub.2 SO.sub.3 4.70    2.37                                                 HAS              5.10    4.00                                                 AC5              0.40    0.72                                                 DEG              12.00   12.00                                                pH               10.3    10.55                                                ______________________________________                                    

A combination of two replenishers like this can cover a wider range ofutilization and so can extend the useful range of an existing PDR.Ideally for this application both the TDR and PDR would be formulated togive the best control of the final tank composition over as wide a rangeof utilization as possible. This would be Case I as outlined above.

In the particular example shown here, the PDR was already fixed to bethat for F:P-2 developer LORR and the TDR was formulated to match this.

In an attempt to predict the behaviour of the PDR at low utilization(5%) in a roller transport processor under various conditions, threecomputer simulation runs were carried out based on data from the ALKREprocessor. The machine and process details are set out in Table 3.

                  TABLE 3                                                         ______________________________________                                        Machine and Process Details                                                                Run 1   Run 2     Run 3                                          ______________________________________                                        Paper replenishment                                                                          19        30        19                                         rate (ml/ft.sup.2)                                                            Average TDR flow                                                                              0         0          20.33                                    rate (ml/hr)                                                                  Average evaporation                                                                            18.86     18.86     18.86                                    rate (ml/hr)                                                                  Average extra water                                                                          18        18         0                                         addition                                                                      Developer volume (l)                                                                         44        44        44                                         Machine speed (in/min)                                                                       13        13        13                                         Machine width (in)                                                                           20        20        20                                         Hours per day   8         8         8                                         machine is on (hr)                                                            Days per week   5         5         5                                         machine is on (days)                                                          Utilization (%)                                                                               5         5         5                                         ______________________________________                                    

Runs 1 and 2 use no TDR, and Run 3 uses a higher TDR than would normallybe used. The concentrations of the solutions for each run are tabulatedin respective Tables 4, 5, and 6.

In Run 1, the benzyl alcohol (BzOH), sulphite, hydroxylamine (HAS) andtriethanolamine (TEA) fall to zero and CD3 is low (see Table 4).

                  TABLE 4                                                         ______________________________________                                        Concentrations of Solutions - Run 1                                                               DEVELOPER                                                            TDR  PDR       Start   End                                         ______________________________________                                        alkali       0.00   20.35     22.90 15.20                                     KBr          0.00   0.00      1.12  1.18                                      TEA          0.00   4.25      2.90  -2.39                                     CD3          0.00   7.10      4.97  2.39                                      BzOH         0.00   18.00     12.60 -2.27                                     K.sub.2 SO.sub.3                                                                           0.00   2.37      1.66  -2.53                                     HAS          0.00   4.00      2.80  -1.37                                     K.sub.2 SO.sub.4                                                                           0.00   8.94      5.94  9.27                                      Phorwite REU 0.00   1.00      0.70  1.04                                      KCl          0.00   0.34      0.24  0.88                                      LiCl         0.00   1.89      1.32  1.96                                      Versa TL73   0.00   0.25      0.17  0.26                                      AC5          0.00   0.72      0.50  0.75                                      DTPA         0.00   0.00      0.00  0.00                                      K.sub.2 CO.sub.3                                                                           0.00   22.40     25.20 23.21                                     pH           0.00   10.55     10.08 9.51                                      DEG          0.00   12.00     8.40  12.44                                     ______________________________________                                    

When the paper replenishment rate is increased from 19 to 30 ml/ft², asin Run 2, the CD3 is brought up to the correct seasoned level (˜4.0),see Table 5, but the bromide, benzyl alcohol, sulphite and HAS levelsare low.

                  TABLE 5                                                         ______________________________________                                        Concentrations of Solutions - Run 2                                                               DEVELOPER                                                            TDR  PDR       Start   End                                         ______________________________________                                        alkali       0.00   20.35     22.90 19.76                                     KBr          0.00   0.00      1.12  0.74                                      TEA          0.00   4.25      2.90  0.10                                      CD3          0.00   7.10      4.97  4.16                                      BzOH         0.00   18.00     12.60 5.33                                      K.sub.2 SO.sub.3                                                                           0.00   2.37      1.66  -0.69                                     HAS          0.00   4.00      2.80  0.65                                      K.sub.2 SO.sub.4                                                                           0.00   8.94      5.94  9.14                                      Phorwite REU 0.00   1.00      0.70  1.02                                      KCl          0.00   0.34      0.24  0.68                                      LiCl         0.00   1.89      1.32  1.93                                      Versa TL73   0.00   0.25      0.17  0.26                                      AC5          0.00   0.72      0.50  0.74                                      DTPA         0.00   0.00      0.00  0.00                                      K.sub.2 CO.sub.3                                                                           0.00   22.40     25.20 22.91                                     pH           0.00   10.55     10.08 9.98                                      DEG          0.00   12.00     8.40  12.27                                     ______________________________________                                    

Thus, simply increasing the replenishment rate does not give asatisfactory result at very low utilization and a complete reformulationwould be necessary to obtain satisfactory results.

By the use of a TDR, as in Run 3, the range of use to low utilization(5%) can be extended, see Table 6.

                  TABLE 6                                                         ______________________________________                                        Concentrations of Solutions - Run 3                                                               DEVELOPER                                                            TDR  PDR       Start   End                                         ______________________________________                                        alkali       12.30  20.35     22.90 19.72                                     KBr          0.00   0.00      1.12  1.08                                      TEA          6.20   4.25      2.90  -2.39                                     CD3          2.15   7.10      4.97  3.86                                      BzOH         18.40  18.00     12.60 12.33                                     K.sub.2 SO.sub.3                                                                           4.70   2.37      1.66  1.38                                      HAS          5.13   4.00      2.80  2.77                                      K.sub.2 SO.sub.4                                                                           6.73   8.94      5.94  13.70                                     Phorwite REU 0.00   1.00      0.70  0.94                                      KCl          0.00   0.34      0.24  0.80                                      LiCl         0.00   1.89      1.32  1.78                                      Versa TL73   0.00   0.25      0.17  0.24                                      AC5          0.40   0.72      0.50  0.99                                      DTPA         0.00   0.00      0.00  0.00                                      K.sub.2 CO.sub.3                                                                           12.50  22.40     25.20 30.92                                     pH           10.32  10.55     10.08 10.07                                     DEG          12.00  12.00     8.40  20.71                                     ______________________________________                                    

Here the TDR is formulated by the method of this invention and also sothat it can be added to approximately take account of water evaporationin the processor.

Run 3 is the same as that in Table 1 and was used in a real machineseasoning run. A control plot of this seasoning run is shown in FIG. 4which maintained consistent sensitometry throughout.

Similar runs without TDR show a fall-off in activity and ultimatelyexhibit process collapse as predicted by the computer simulation model.

A further example showing how the present invention can be applied in aprocess for `Ektacolor` paper is described below.

EXAMPLE 2

A fresh tank of `Ektaprint-2` LORR developer was prepared followinginstructions supplied with the kit.

The composition of the replenisher and time dependent replenisherprepared is shown in Table 7:

                  TABLE 7                                                         ______________________________________                                        Time dependent replenisher and                                                replenisher formulation                                                       Component            Amount per liter                                         ______________________________________                                        Benzyl alcohol       19.5     ml                                              Diethylene glycol    12.0     ml                                              Triethanolomine (100%)                                                                             5.3      g                                               Hydroxylamine sulphate                                                                             4.7      g                                               Potassium chloride   3.16     g                                               Versa TL 73          0.28     g                                               Potassium bromide    1.15     g                                               CD-3                 4.35     g                                               Potassium sulphite   3.05     g                                               Phorwite REU         0.7      g                                               Potassium hydroxide (48%)                                                                          8.6      g*                                              Antical 5            0.8      ml                                              Potassium carbonate  22.4     g                                               ______________________________________                                         *adjustable to pH 10.08                                                  

A paper dependent replenisher was prepared as shown in Table 8:

                  TABLE 8                                                         ______________________________________                                        Paper dependent replenisher formulation                                       Component      Amount per liter                                               ______________________________________                                        CD-3           65.0 g                                                         Potassium sulphite                                                                           2.75 g                                                         ______________________________________                                    

`Ektacolor` paper, 22% exposed to D_(max), was processed in thedeveloper and was replenished as follows:

The time dependent replenishment rate during the day was 147.5 ml/hr andat night or when the machine is off was 67.5 ml/hr. The paper dependentreplenisher was added at 1 ml/ft² and the replenisher (same formulationas the time dependent replenisher) at 12.5 ml/ft².

The paper dependent replenisher was added such that it went into emptyspace and the replenisher and time dependent replenisher were addedafter the machine had been topped up with water and so always replacedtank developer.

`Ektacolor` and `Ektaprint`, referred to above, are trade marks.

It is to be noted that the present invention is not limited to use withcolour developer soultions as described in the examples, but couldequally well be used for black and white developer solutions.

Furthermore, the present invention could be used for any other solutionwhere components are lost due to evaporation or oxidation.

We claim:
 1. A method of replenishing photographic processing solutions,containing water and one or more components, in photographic processingapparatus in which one or more components are lost from the processingsolution by oxidation or evaporation, characterized in that thereplenishment rate for a particular component in a given solution isdetermined as a function of water evaporation rate from the apparatus.2. A method according to claim 1, wherein the function for any givensolution is determined by measuring component loss rates for thatsolution for different water evaporation rates.
 3. A method according toclaim 1 or 2, wherein the determined function for that particularcomponent in a given solution is applicable to any processing apparatususing that given solution.
 4. A method according to claim 1, wherein thewater evaporation rate is proportional to the effective surface area. 5.A method according to claim 1, wherein the function is substantiallylinear.
 6. A method according to claim 1, further including areplenishment in accordance with throughout of material being processed.